The present invention relates to a writing instrument, in particular to a ballpoint pen, whose refill with a pen tip can be projected from and retracted into the front end opening of the pen barrel by the operation of the actuating mechanism.
Conventionally, a plunger type ball-point pen, whose pen tip can be projected from and retracted into the front end opening of the pen barrel, is well known. The structure of the plunger type ballpoint pen is as follows: there is a freely-sliding expendable ballpoint pen refill in the pen barrel; the expendable ballpoint pen refill has a tendency of moving toward the upper part of the pen barrel under the force of a spiral spring; a wheel actuating mechanism for the plunger type refill is mounted at the rear end of the ballpoint pen refill; the actuating mechanism consists of a plunger projecting out of the upper opening of the pen barrel, several terraced oblique plane structures on the interior wall of the pen barrel and grooves formed between said structures, a wheel part provided at the front end of the plunger with a projection slidable along said grooves and a wheel with its projection biased connected to the projecting rib when engaged with said wheel part so that the wheel may rotate between said grooves or said terraces. The wheel rotates in a predetermined direction with the depression of the plunger and springs back due to the spiral spring. But with the deflection of the wheel, the tip of the expendable ballpoint pen refill is projected from and retracted into the front end opening of the pen barrel.
Another existing type of retractable pen is similar to the above type, whose pen tip is projected and retracted through the mutual press engagement of the upper and lower part of the pen barrel.
The object of the present invention is to provide a pen with a new structure for projecting and retracting pen tip.
In order to achieve the above object, the pen of the present invention converts the rotation of a gear to a linear motion of the slider along a pen barrel by means of a connecting rod off-axially connected to the rotatable gear.
The present invention provides a writing instrument with a retractable pen tip mechanism, characterized in that it comprises: an expendable refill having a front end as the pen tip, a pen barrel which has a front end opening and accommodates said refill, a slider positioned at the rear end of the refill and slidable in the cavity inside said pen barrel, a connecting rod with one end pivotally connected to said slider, an inner gear mounted inside the pen barrel and off-axially and pivotally connected with said connecting rod, and an outer gear mounted inside of the pen barrel and engaged with said inner gear.